[clang] [llvm] [RISCV][MC] MC layer support for the experimental zalasr extension (PR #79911)

[Philip Reames via cfe-commits]

preames wrote:

I think we need some kind of official documentation to merge this.  I went looking to see if I could find mention of this extension in e.g. ARC notes, and didn't find it.  @mehnadnerd can you provide some kind of link or reference to some RVI source indicating the status of this proposal?  It doesn't need to be near ratified, I'm just worried about the precedent we'd set by accepting an experimental extension with the only reference being an individual person's github.  

https://github.com/llvm/llvm-project/pull/79911